Method and apparatus for identifying disruptions to fluid communication between an extracorporeal circuit and a patient's circulatory system - Patents.com

Abstract

A system and method for identifying disruptions to flow from an extracorporeal circuit to a patient's circulatory system (e.g., IV needle removal or access-bloodline separation) based on extracorporeal circuit flow data. The occurrence of such disruptions can be assessed by identifying and monitoring patient contributions to the flow data as harmonics. The system can identify non-harmonic changes (e.g., spikes) in the extracorporeal circuit flow and can use the non-harmonic changes alone or in combination with the identified harmonics to assess the occurrence of a disruption. The system can use spikes in blood flow as well as spikes in dialysate flow fluidly connected to the extracorporeal circuit as spikes to identify such disruptions.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 17 / 387,391, filed on July 28, 2021, entitled "METHOD AND APPARATUS FOR IDENTIFYING DISRUPTION OF A FLUID CONNECTION BETWEEN AN EXTRACORPOREAL CIRCUIT AND A PATIENT CIRCULATORY SYSTEM," the entire disclosure of which is incorporated herein by reference.

[0002] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not applicable.

[0003] Names of parties to the joint research agreement Not applicable.

[0004] Sequence Listing Reference Not applicable.

[0005] Statement of Prior Disclosure by Inventor or Co-Inventors Not applicable. [Technical field]

[0006] The present disclosure relates to an apparatus and method for detecting a disruption of fluid communication between an extracorporeal circuit and a patient's circulatory system, particularly for detecting a disruption in an extracorporeal circuit downstream of a blood pump of a blood treatment device, including, but not limited to, a venous needle withdrawal (VND) or an access-to-bloodline separation (ABLS).More particularly, the present disclosure relates to an apparatus and method for identifying a disruption between a venous line of an extracorporeal circuit and a patient's circulatory system in response to a change in the patient's contribution to flow data of the extracorporeal circuit, particularly the venous line. [Background technology]

[0007] Medical procedures involving the delivery of fluids to, through, or from a patient, or any combination thereof, can range from procedures involving the transfer of blood between a patient and an extracorporeal system connected to the patient via a needle, multiple needles, or catheters inserted into the patient. For example, hemodialysis, hemofiltration, and hemodiafiltration are all treatments that remove waste products, toxins, and excess water from the blood. In these treatments, the patient is connected to an extracorporeal circuit and equipment, and blood is pumped through the extracorporeal circuit and equipment, which removes waste products, toxins, and fluids from the blood and returns the cleaned blood to the patient.

[0008] In these treatments, access devices such as needles and catheters are inserted into the patient's vascular system to allow blood to flow to and from equipment outside the body. Conventional hemodialysis, hemofiltration, and hemodiafiltration treatments can take hours, days, or even weeks, and are typically performed in a treatment facility. When treatment is performed in a treatment facility, the patient is visually monitored during hemodialysis, for example, to detect whether the needle has become dislodged. However, the needle may be in a position that is difficult for the patient or medical staff to see (e.g., when covered by a blanket), and any interruption may be detected late, which may prevent appropriate action from being taken in a timely manner.

[0009] There has also been renewed interest in self-care and home therapies such as home hemodialysis due to improved quality of life, reduced morbidity and mortality, and reduced costs compared to center-based treatments. These home therapies (whether hemodialysis, hemofiltration, or hemodiafiltration) can be performed during the day, evening, or even at night. In unsupervised situations or while the patient is asleep, there is an increased risk of disconnection due to the absence of a caregiver, and the patient may not even notice that the connection has been disconnected.

[0010] However, dialysis is a complex procedure that has traditionally been the work of a team of highly skilled professionals responsible for providing safe and effective care to patients. Recently, patients have been able to self-manage dialysis at home. However, there remain many situations that can lead to complications during dialysis. Many of these potential problems are contained by safety devices, such as alarm circuits built into dialysis machines, but needle dislodgement (including needle displacement) can go undetected or be detected very late.

[0011] In extracorporeal blood treatment, it is important to minimize the risk of an extracorporeal circuit malfunction, since such malfunction may be life-threatening for the patient. If the extracorporeal circuit is interrupted downstream of the blood pump, for example by a venous needle dislodgement (VND) from the patient or the patient access, or by a central venous catheter (CVC) or venous fistula from the hemodialysis blood line used in the treatment (access-bloodline separation), serious consequences may occur. Such an interruption may result in the loss of blood from the patient within minutes.

[0012] Specifically, for example, the connection between the extracorporeal circulation and the venous access may be impeded if the needle or cannula becomes dislodged and the connection between the extracorporeal circulation and the patient is not properly established or is cut off. In such cases, problems may arise, especially if the venous access to the patient's vascular system becomes dislodged. If the dislodgment of the venous access cannot be detected in a timely manner, blood will continue to be drawn from the patient via the arterial access, but blood after extracorporeal blood therapy will not be properly returned to the patient. For example, with a typical blood flow rate of 300 to 400 mL / min, the patient will fall into a critical condition within a few minutes.

[0013] Conventionally, the removal of an intravenous needle during blood processing could be detected based on a pressure signal from a pressure sensor ("venous pressure sensor") located downstream of the blood pump in the extracorporeal circuit. However, the pressure in the extracorporeal circuit can vary from treatment to treatment and can also change during treatment, for example due to the patient's movements during treatment, making it difficult to set an appropriate threshold. Furthermore, if the detached extracorporeal circuit gets caught on the bedsheets or the patient's clothing during treatment, the pressure measurement may not change sufficiently to indicate a potentially dangerous situation. Summary of the Invention [Problem to be solved by the invention]

[0014] Thus, a need exists for improved systems and methods for detecting disruptions in fluid communication between an extracorporeal circuit and a patient's circulatory system, particularly for detecting disruptions in an extracorporeal circuit downstream of a blood pump of a blood treatment device, including, but not limited to, access-blood line separation (ABLS), intravenous needle dislodgement (VND), and lost connection to a catheter. [Means for solving the problem]

[0015] In general, the present disclosure provides an apparatus for monitoring an extracorporeal circuit extending from a patient's blood withdrawal site through an extracorporeal blood treatment device and back to a patient's blood inlet site. The extracorporeal circuit includes a blood withdrawal line extending from the patient's blood withdrawal site to the blood treatment device, a blood inlet line extending from the blood treatment device to the patient's blood inlet site, and a pump operable to pump blood through the extracorporeal circuit from the blood withdrawal line, through the blood treatment device, through the blood inlet line, and to the patient's blood inlet site. The apparatus also includes a flow sensor configured to obtain flow data of blood flow in at least one of the blood withdrawal line and the blood inlet line, and a controller in communication with the flow sensor. The controller is configured to identify a patient contribution to the flow data that is derived from the patient's physiology, and to detect a disruption in the extracorporeal circuit based at least in part on the identified patient contribution.

[0016] In one configuration, the present disclosure provides a monitoring apparatus for monitoring an extracorporeal blood circulation circuit extending from a vascular access through an extracorporeal blood treatment device and back to the vascular access, the extracorporeal blood circulation circuit including an arterial line as a blood-out line extending from the vascular access to the blood treatment device, a venous line as a blood-inlet line extending from the blood treatment device to the vascular access, and a pump operable to pump blood through the extracorporeal blood circulation circuit from the arterial line, through the blood treatment device, through the venous line, and to the vascular access. The monitoring apparatus also includes a flow sensor configured to acquire flow data of blood flow in the venous line, and a controller in communication with the flow sensor. The controller is configured to (i) identify a patient contribution to the flow data in the acquired flow data that is attributable to downstream patient physiology, and (ii) detect a flow disruption between the extracorporeal blood circulation circuit and a patient based at least in part on the identified patient contribution. It is further disclosed that the control device is capable of (i) determining a flow rate in the venous line based on the acquired flow data, (ii) identifying a patient contribution to the flow rate in the determined flow rate that is due to downstream patient physiology, and (iii) detecting a flow interruption between the extracorporeal blood circulation circuit and the patient based at least in part on the identified patient contribution.

[0017] The present disclosure also contemplates that disruptions may be identified by obtaining arterial (exit) line flow data in addition to or in lieu of venous (inlet) line flow data, and may also be identified by comparing or correlating venous and arterial line flow data and from changes in such comparison or correlation of flow data.

[0018] The present disclosure also contemplates that the control device is connected to a flow sensor that senses flow data through the venous (blood inlet) line of the extracorporeal circuit, and is configured to identify a disruption of blood flow downstream of the flow sensor in response to a change or loss of patient contribution to the venous line flow data.

[0019] Also disclosed is a method that includes identifying a disruption in connection between the venous (blood infusion) line of the extracorporeal circuit and the patient's circulatory system in response to a change or loss of patient contribution to venous line flow data.

[0020] A further method includes identifying a patient contribution in measured flow data in the venous (blood infusion) line of an extracorporeal circuit that stems from downstream patient physiology and monitoring the patient contribution to identify disruptions to vascular access.

[0021] Also provided is an additional method including the steps of measuring flow data in a venous line in an extracorporeal circuit having a pump providing flow to the venous (blood supply) line, and identifying a disruption between the venous line and the circulatory system in response to a change in a component in the measured flow data that corresponds to a physiological parameter of a circulatory system connected downstream to the venous line.

[0022] The present disclosure also includes a method for monitoring an extracorporeal blood treatment device with an extracorporeal blood circulation circuit having an arterial blood line with a patient arterial connection, a venous blood line with a patient venous connection, and a pump for transporting blood through the extracorporeal blood circulation circuit, the method including the steps of measuring blood flow data in the venous blood line of the extracorporeal blood circulation circuit, identifying a patient contribution in the measured blood flow data that corresponds to a downstream patient physiological parameter, determining the occurrence of a flow interruption between the extracorporeal circulation circuit and the patient's circulatory system in response to a change or disappearance of the patient contribution to the measured blood flow data, and generating a control signal to activate an alarm unit, stop the pump, or both after determining the occurrence of the interruption.

[0023] In a further configuration, the present disclosure provides an apparatus for monitoring an extracorporeal circuit extending from a patient's circulatory system through a patient's blood withdrawal site to an extracorporeal blood treatment device, through a patient's blood inflow site, and back to the patient's circulatory system. The extracorporeal circuit includes a blood withdrawal line extending from the patient's blood withdrawal site to the blood treatment device, a blood inflow line extending from the blood treatment device to the patient's blood inflow site, and a pump configured to pump blood through at least a portion of the extracorporeal circuit. The apparatus also includes a flow sensor configured to obtain flow data of blood flow in the portion of the extracorporeal circuit, and a controller in communication with the flow sensor. The controller is configured to detect a disruption between the extracorporeal circuit and the patient's circulatory system based at least in part on a non-harmonic increase in blood flow in at least one of the blood withdrawal line and the blood inflow line.

[0024] The present disclosure also includes a control device connected to a flow sensor providing flow data of blood flow through a blood supply line of the extracorporeal circuit, the control device being configured to identify disruptions to blood flow from the extracorporeal circuit to the patient's circulatory system in response to non-harmonic changes in blood flow in the provided flow data.

[0025] Additionally, an additional method is provided that includes identifying a disruption in communication between a blood line of the extracorporeal circuit and a patient's circulatory system in response to a non-harmonic increase in flow rate in the extracorporeal circuit.

[0026] Hereinafter, the embodiments of the present disclosure will be described, but it should be understood that the present disclosure is not limited to the embodiments described in the present description, and various modifications are possible without departing from the basic principles of the present invention. Therefore, the scope of the present disclosure should be limited only by the scope of the attached claims. [Brief description of the drawings]

[0027] [Figure 1] Schematic showing typical extracorporeal circuits and access devices for connection to a patient's circulatory system. [Diagram 2] Flow rate vs. time graph for venous line of extracorporeal circuit [Diagram 3] Flow vs. time graph for the arterial line of an extracorporeal circuit [Figure 4] A frequency graph showing the results of a spectrum analysis of the measured flow rate of the venous line of an extracorporeal circulation circuit. [Diagram 5] A frequency graph showing the results of a spectrum analysis of the measured flow rate in the arterial line of an extracorporeal circulation circuit. [Figure 6] A frequency graph showing the results of a spectrum analysis of the measured flow rates of the arterial and venous lines of an extracorporeal circuit. [Figure 7] A second flow rate versus time graph for the venous line of the extracorporeal circuit. [Figure 8] A second flow versus time graph for the arterial line of the extracorporeal circuit. [Figure 9] FIG. 8 is a frequency graph showing the results of a spectrum analysis (FFT) of the measured flow rate of the venous line of the extracorporeal circuit shown in FIG. 7, in which harmonics originating from the physiological function of the patient are shown. [Figure 10] A frequency graph showing the results of spectrum analysis (FFT) for the measured flow rate in the arterial line of the extracorporeal circuit shown in Figure 8. [Figure 11] A graph showing non-harmonic changes (e.g., spikes) in flow rate in the venous line of an extracorporeal circuit that occur as the venous needle is removed. [Figure 12] Schematic diagram showing the extracorporeal circuit and the patient's circulatory system [Figure 13] 1 is a flowchart of a process for identifying a disruption between an extracorporeal circuit and a patient's circulatory system. [Figure 14] 1 is a flow chart illustrating the configuration of a controller for identifying a disruption between an extracorporeal circuit and a patient's circulatory system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] 1 and 12, an extracorporeal circuit ("EC circuit") 100 is shown connected to a patient's circulatory system 30.

[0029] The extracorporeal circuit 100 extends from a blood withdrawal site 110 of the patient, through a blood treatment device 130, and back to a blood transfer site 160 of the patient. The blood withdrawal site 110 of the patient can be a part of the patient's circulatory system 30, or a part connected to the patient's circulatory system 30. The blood transfer site 160 of the patient can be a part of the patient's circulatory system, or a part connected to the patient's circulatory system. The extracorporeal circuit also includes a blood withdrawal line 120 extending from the patient's blood withdrawal site to the blood treatment device, a blood transfer line 150 extending from the blood treatment device to the patient's blood transfer site, and a pump 170. The pump 170 is configured to pump blood through the extracorporeal circuit, from the blood withdrawal line, through the blood treatment device, through the blood transfer line, and to the patient's blood transfer site. The flow sensor is configured to acquire blood flow data from at least one of the blood withdrawal line 120 and the blood transfer line 150. In a particular configuration, flow sensor 126 obtains flow data for blood removal line 120 and flow sensor 156 obtains flow data for blood inlet line 150. Controller 180 is connected to at least one of flow sensors 126, 156 and pump 170.

[0030] In one configuration, the extracorporeal circuit 100 is configured to perform dialysis. In that case, the blood removal line 120 is referred to as an arterial line, the blood treatment device 130 includes, but is not limited to, a dialyzer, and the blood delivery line 150 is referred to as a venous line. For purposes of this specification, blood travels from the access device 200 to the arterial line 120 and back to the access device on the venous line 150. Note that although the extracorporeal circuit 100 is shown in the figures as having both an arterial flow sensor 126 and a venous flow sensor 156, it should be understood that the system of the present disclosure may be implemented without or with the arterial flow sensor.

[0031] In one configuration, the extracorporeal circuit 100 is fluidly connected to a dialysate side 302 of a blood treatment device 130, such as a dialyzer, as shown in FIG. 1. In FIG. 1, a dialysate circuit 310, as known in the art, includes a dialysate inlet line 320 to the dialyzer, a dialysate outlet line 330 from the dialyzer, a pump 340, and associated control, replenishing, and balancing mechanisms, which are shown diagrammatically with reference numeral 350. Additionally, the dialysate circuit 310 may further include a dialysate inlet flow sensor 326 configured to sense the flow rate of the dialysate inlet line 320, and a dialysate outlet flow sensor 336 configured to sense the flow rate of the dialysate outlet line 330. Note that the dialysate inlet and outlet flow sensors may be similar to flow sensors 126, 156 described below.

[0032] In dialysis terminology, blood travels from the patient's blood withdrawal site 110 to an arterial line 120 (blood withdrawal line), passes through a venous line 150 (blood transfer line), and returns to the patient's blood transfer site 160. In dialysis terminology, the flow sensor 126 that acquires flow data in the arterial line is called an arterial flow sensor 126, and the flow sensor 156 that acquires flow data in the venous line is called a venous flow sensor 156.

[0033] It should be understood that although the system is shown in the figures as having both an arterial flow sensor 126 and a venous flow sensor 156, the present disclosure may be practiced using only the arterial flow sensor 126, only the venous flow sensor 156, or both the arterial and venous flow sensors.

[0034] As discussed above, in one configuration, the extracorporeal circuit 100 is configured to perform extracorporeal blood therapy, in which the extracorporeal circuit 100 may be part of a blood treatment device 130 that removes blood from a patient, processes (e.g., treats) it, and then reintroduces it back into the patient. Thus, in one configuration, the extracorporeal circuit includes both the dialysate circuit 310 and the blood side (including the arterial line 120 and the venous line 150) along with the blood treatment device 130.

[0035] Extracorporeal blood therapies include hemodialysis, hemodiafiltration, hemofiltration, plasma exchange, and the like, including the removal of toxins from the blood, such as by diffusion through a membrane.

[0036] The following terms are used in the present specification: The term "flow rate data" refers to any data from which flow rate can be derived, estimated, or calculated, and any surrogate data from which flow rate can be derived, estimated, or calculated. It is also contemplated that flow rate can be actual, calculated, or predicted blood flow, as well as any surrogate value for actual blood flow. Such surrogates include, but are not limited to, flow velocity, values ​​proportional to, or related to blood flow or flow velocity. Flow data encompasses any signal or data related to blood flow, particularly any signal or data related to the pulsatility, variability, frequency dependence, or oscillatory content or characteristics of blood flow. Flow data can be represented by any signal, such as, but not limited to, optical, acoustic, electromagnetic, temperature, or other signals on which frequency analysis can be performed. Thus, flow data includes any signal or data indicative of flow or on which flow rate, or pulsations, fluctuations, frequency fluctuations, or oscillations in flow rate, or pulsations, fluctuations, frequency fluctuations, or oscillations in flow rate, or corresponding surrogate data. For example, blood markers, such as particles native to the blood or particles introduced into the blood, may be used as surrogate data. Thus, the term flow rate is intended to encompass any value or measurement that corresponds to, is a surrogate for, or can represent, blood flow or dialysate flow, respectively (and in particular, pulsations, fluctuations, frequency fluctuations, oscillations, or characteristics or properties of blood flow or dialysate flow, respectively). Thus, the term "flow rate" (which encompasses "blood flow rate" and "dialysate flow rate") encompasses volumetric flow rate, which is a measurement of the volume of fluid passing through a cross-sectional area of ​​a conduit per unit time, and can be expressed in units of volume per unit time (typically milliliters / minute (mL / min) or liters / minute (L / min)) or any surrogate thereof.It should be appreciated that flow rates, such as blood flow and dialysate flow, can be measured and calculated by any of a variety of known systems and methods for use with flow sensors 126, 156, 326, 336.

[0037] The access device 200 is fluidly connected to a patient's circulatory system 30, such as a human (or animal) circulatory system. The patient's circulatory system 30 includes blood, a vascular system with a cardiopulmonary system, a systemic system connecting the cardiopulmonary system to the tissues of the body, and the heart. Specifically, the systemic system pumps blood throughout the patient's body via a vascular system (arteries, veins, capillaries). Thus, the access device 200 provides access to the extracorporeal circuit 100 by fluidly connecting to the patient's circulatory system 30. The term "access device" encompasses any access to the patient's circulatory system 30, including, but not limited to, catheters, needles, shunts, AV native fistulas, AV-artificial grafts, and venous catheters or other vascular implants. The connection of the extracorporeal circuit 100 to the patient via the access device 200 is typically a catheter or cannula or needle, e.g., a dialysis cannula, where fluid communication is established, e.g., by puncturing the access device 200. As used herein, the access device 200 encompasses the patient's blood withdrawal site 110 and the patient's blood infusion site 160. Thus, the access device 200 includes arterial and venous accesses that are separate from one another, as well as arterial and venous accesses that are proximal or adjacent to one another, or within a common shunt, line, or graft.

[0038] The term "blood treatment" refers to any blood treatment, including but not limited to dialysis. Dialysis also includes toxin removal, such as by diffusion therapy, including but not limited to hemofiltration, hemodialysis, hemodiafiltration, or Continuous Renal Replacement Therapy (CRRT). A blood treatment device is any device for performing blood treatment. Thus, in one configuration, a blood treatment device, such as a dialyzer, can be configured to controllably transfer solutes and water through a semipermeable membrane that separates the blood flow from the dialysate flow. Such transfer processes include diffusion (dialysis) and convection (ultrafiltration). Blood treatment devices can also perform any of a number of other blood treatments, such as chemical, electromagnetic, and thermal treatments.

[0039] The term blood includes processed or unprocessed blood, including synthetic and natural blood, as well as plasma.

[0040] The term "disruption" encompasses any diversion, disconnection, dislodgement, or interruption in the flow between the extracorporeal circuit 100 and the patient's circulatory system 30. Disruptions, such as, for example, venous needle dislodgement or dislodgment, may occur downstream of the pump 170, downstream of the blood treatment device 130, and between the extracorporeal circuit 100 and the access device 200, or between the access device and the patient's circulatory system 30 (including the patient's blood withdrawal site 110 and the patient's blood inlet site 160). Thus, the term "disruption" includes, but is not limited to, "venous needle dislodgement (VND)" in which an venous needle is dislodged from a patient or patient access, or "access-to-bloodline separation (ABLS)" in which a central venous catheter (CVC) or venous fistula is dislodged from a hemodialysis blood line being used for treatment.

[0041] The term "controller" includes signal processors and computers, including pre-programmed desktop or laptop computers, or dedicated processors. Such controllers can be easily programmed to perform the calculations described herein or their derivations to determine flow rate and convert flow data as described herein. The controller can also perform preliminary signal conditioning, such as summing one signal with another signal, or summing one signal with a portion of another signal.

[0042] The term "flow sensor" encompasses any sensor device that provides a signal representative of flow data or that provides data upon which a flow rate, flow pulsation, fluctuation, frequency change, or vibration, or a proxy for the flow rate, flow pulsation, fluctuation, frequency change, or vibration, can be determined or sensed.

[0043] The term "upstream" of a location refers to the direction against blood flow away from the location, and the term "downstream" of a location refers to the direction of blood flow away from the location. The "arterial line" or arterial line side is the portion of the extracorporeal circuit 100 through which blood flows from the patient's blood withdrawal site 110 (e.g., access device 200) to the blood treatment device 130. The "venous line" or venous line side is the portion of the extracorporeal circuit 100 through which blood flows from the blood treatment device 130 to the patient's blood infusion site 160 (e.g., access device 200).

[0044] Generally, circulation of blood through the extracorporeal circuit 100 is accomplished by a pump 170. The present disclosure encompasses extracorporeal circuits 100 in which blood treatment devices 130 (such as an extracorporeal membrane oxygenator (ECMO)) remove blood from a venous portion of a patient's circulatory system 30 and return treated (oxygenated) blood to a second venous portion of the patient's circulatory system, as well as configurations in which blood is removed from either a venous or arterial portion of a patient's circulatory system and returned to either a venous or arterial portion of the patient's circulatory system, with it being understood that detection of disruptions may be accomplished in any of these configurations.

[0045] It is also contemplated that the present disclosure encompasses an extracorporeal circuit 100 having multiple patient withdrawal sites 110, multiple blood withdrawal lines 120, multiple blood treatment devices 130, multiple pumps 170, multiple blood delivery lines 150, and multiple patient blood delivery sites 160, or any combination thereof. Thus, the system may have more than one blood delivery line 150 to the patient. It is understood that for certain types of extracorporeal blood treatments, the extracorporeal circuit 100 includes an arterial needle for withdrawal and a venous needle for delivery, which are inserted into the access device 200. Thus, in an optional configuration, the extracorporeal circuit 100 is configured to withdraw blood from the access device 200 and deliver the withdrawn blood back to the access device 200. The withdrawn blood may then be treated while it is withdrawn, e.g., while it is passing through the dialyzer 130 before being delivered back to the access device 200 via the venous line 150.

[0046] In one configuration, blood passes from access device 200, through pump 170, and to a blood treatment device 130, such as a dialyzer. The blood is then pumped from blood treatment device 130 to access device 200. Although not shown, it is contemplated that venous line 150 may include an air trap and air detector between blood treatment device 130 and access device 200.

[0047] Depending on the configuration of the extracorporeal circuit 100 and the method of measuring blood parameters, an introduction port as a site for introducing a substance into the extracorporeal circuit 100 may be provided in the arterial line 120 or may be provided in the arterial line 120 .

[0048] The venous line 150 connects the flow of the extracorporeal circuit 100 to the circulatory system 30, such as via the access device 200. Typically, the venous line 150 includes a return (venous) cannula that provides a fluid connection to the access device 200.

[0049] The venous line 150 includes a flow sensor 156. The flow sensor 156 measures flow characteristics or parameters to generate flow data from which the flow rate or any pulsation, fluctuation, frequency change, or oscillatory components in the flow or frequency components of the flow can be determined. Thus, the flow sensor 156 can include a flow sensor for sensing the passage of an indicator through the extracorporeal circuit 100, an ultrasonic sensor, and / or a dilution sensor. The flow sensor 156 can be any of a variety of sensors for obtaining flow rate data. In an optional configuration, the flow sensor 156 (and the sensor 126) can measure various blood characteristics, including, but not limited to, temperature, Doppler frequency, electrical impedance, optical properties, density, ultrasonic velocity, glucose concentration, oxygen saturation, or other blood substances (any physical, electrical, or chemical blood properties). Alternatively, additional sensors (not shown) can be provided in addition to the flow sensor 156 to measure selected blood characteristics or properties.

[0050] As noted in the description of flow sensor 156, flow sensor 126 in arterial line 120 can be any of a variety of sensors. Although the system is described herein as having two flow sensors 126, 156, it is understood that this is for accuracy purposes and that a single flow sensor would be sufficient. It is further contemplated that pump operating parameters, such as the pump's revolutions per minute (RPM), can identify the pulsation imparted to the flow by pump 170, thereby allowing the pump contribution to be distinguished from the patient contribution.

[0051] Specifically, when the arterial line 120 is provided with a flow sensor 126, the flow sensor 126 can be any of a variety of sensors that obtain flow data. The flow sensor 126 can measure various blood characteristics, including but not limited to temperature, Doppler frequency, electrical impedance, optical properties, density, ultrasonic velocity, glucose concentration, oxygen saturation, or blood substance (any physical, electrical, or chemical blood property) that are related to, correspond to, or are indicative of blood flow and pulsation, vibration, fluctuations, frequency changes in flow, or time variations in flow. It is also understood that the flow sensor 126 can measure blood flow. Thus, in one configuration, the system includes one blood property sensor and one flow sensor. Additionally, a combination sensor that measures flow and blood parameters (characteristics) can be used.

[0052] It is also understood that the flow sensors 126, 156 can be located external to the extracorporeal circuit 100, i.e., the flow sensors 126, 156 can be located in a remote location and measure changes in the blood since the introduction of the indicator or a value related to the introduction of the indicator in the extracorporeal circuit 100 and communicate or transmit this to the respective sensors by means of diffusion, electromagnetic fields, thermal fields, etc. It is contemplated that the flow sensors 326, 336 can be any of the embodiments described for the flow sensors 126, 156.

[0053] The pump 170 may be any of a variety of pump types, including but not limited to a peristaltic pump, roller pump, impeller pump, or centrifugal pump. The pump 170 generates a blood flow rate through the extracorporeal circuit 100. Depending on the particular configuration, the pump 170 may be controlled to establish a predetermined blood flow rate in the extracorporeal circuit 100 by direct control of the pump itself or via the controller 180. The location of the pump 170 may be any of a variety of locations within the extracorporeal circuit 100, including but not limited to the location shown in FIG. 1. In one configuration, the pump 170 is a commercially available pump that may be set or adjusted to provide any of a variety of flow rates. This flow rate may be read by a user, transmitted to and read by the controller 180, or both.

[0054] Normal (forward) blood flow through the extracorporeal circuit 100 includes blood flow removing blood from the access device 200 through the arterial line 120, blood flow sending the removed blood to the extracorporeal circuit (for treatment of the blood in the dialyzer 130), and blood flow introducing the removed (or treated) blood into the access device through the venous line 150. A pump 170 can generate blood flow from the access device 200 through the extracorporeal circuit 100 and back to the access device.

[0055] Typically, controller 180 may be connected to blood treatment device 130, pump 170, and flow sensor 156 and flow sensor 126 (if flow sensor 126 is used). Controller 180 may be a stand-alone device, such as a personal computer, a dedicated device, or may be integrated into one of the components, such as pump 170 or blood treatment device 130. Although controller 180 is shown as being connected to flow sensors 126, 156, pump 170, and blood treatment device 130, it should be understood that controller 180 may be connected to only the flow sensors, the sensors and the pump, or any combination of the flow sensors, the pump, and blood treatment device 130.

[0056] It has been discovered that the venous line flow data, including the flow rate of the venous line 150, not only pulsates at a frequency generally derived from the pump 170, but also contains a component corresponding to the physiological function of the patient downstream from the measurement location of the venous line flow data. That is, the venous line 150 flow data, and therefore the flow rate of the venous line 150, contain a contribution from the patient, and at least a portion of the patient contribution to the acquired flow data is due to physiological functions inside the patient further downstream. Such a patient contribution is believed to include a component derived from the pulsation of the patient's circulatory system 30 and a respiratory component. Since the flow through the extracorporeal circuit 100 is generated by the pump 170 and the patient's physiological functions are downstream from the venous line 150, it was a surprising discovery that the venous line flow rate contains a contribution from the patient. Furthermore, as described below, it has also been discovered that the arterial line 120 flow data also contains a patient contribution, and at least a portion of the patient contribution to the acquired flow data is due to physiological functions inside the patient.

[0057] The patient contribution to the flow data arises from the patient's physiology and propagates through the access device 200. For example, if the access device is an arteriovenous (AV) shunt, it propagates through a needle, or if the access device is a catheter connected to the circulatory system 30, it receives a contribution from a central vein (or heart). It has been determined that the patient contribution can be observed in the flow data (e.g., blood flow) in the extracorporeal circuit 100, particularly in the form of pulsatile flow in both the arterial line 120 and the venous line 150. It is noted that the patient contribution observed in the arterial line 120 is primarily transmitted from the arterial access of the extracorporeal circuit 100, and that flow data can be obtained in the arterial line. It is also noted that any patient contribution propagating upstream from the venous line 150 to the arterial line 120 must propagate through the pump 170, the blood treatment device 130 (e.g., a dialyzer), and a bubble trap (if present), each of which substantially attenuates the manifestation of the patient contribution from the venous access. That is, the patient contribution propagating upstream along venous line 150 is substantially attenuated as it propagates through pump 170, blood treatment device 130, and bubble trap (if present) into arterial line 120. Thus, the majority of the patient contribution contained in the flow data obtained from arterial line 120 is that transmitted downstream from the patient through arterial line 120. Similarly, the majority of the patient contribution observed in venous line 150 is the patient contribution that propagated upstream along venous line 150 from access device 200. Any patient contribution propagating downstream along arterial line 120 is substantially attenuated as it propagates through pump 170, blood treatment device 130, and bubble trap (if present) into venous line 150. That is, any patient contribution propagating downstream from the arterial line 120 to the venous line 150 is substantially attenuated by the pump 170, the blood treatment device 130 (dialyzer), and the bubble trap (if present), so that the patient contribution included in the flow data for the venous line 150 is dominated by the patient contribution propagating upstream along the venous line from the access device 200 (e.g., needle, venous catheter lumen, etc.).Thus, if an interruption or break occurs in the arterial access, the pump 170 will suck in air and stop blood flow through the extracorporeal circuit 100. On the other hand, if an interruption or break occurs in the venous line 150, the flow in the arterial line 120, and therefore the patient contribution in the arterial line, will not change significantly, providing a more reliable indication of the occurrence of an interruption in the venous line.

[0058] The controller 180 is programmed to identify the patient contribution to the flow data (e.g., in the blood flow rate in the venous line 150) and compare the patient contribution to the flow data between two different points in time, or to identify a change in the patient contribution in the flow data or measured flow (e.g., when the change in the patient contribution reaches a predetermined level or when the patient contribution is lost).

[0059] As shown in FIG. 2, venous flow pulsates at a frequency of approximately 68 beats per minute, which correlates with the patient's heart rate.

[0060] 3, if pump 170 is a peristaltic or roller pump type, the flow rate in arterial line 120 will pulsate and be strongly influenced by the flow fluctuations caused by pump 170. The approximately 48 beats per minute pulsation caused by pump 170 can also be determined or known from the revolutions per minute of pump 170, or from the revolutions per minute of blood treatment device 130 if pump 170 is incorporated into the blood treatment device.

[0061] It has been found that spectral analysis of the flow data in the venous line 150 can identify various contributions to the pulsatile flow rate of the extracorporeal circuit 100, including the pump contribution from the pump 170 and the patient contribution. Analysis of flow data, such as the measured flow rate, generally identifies the strength of the input signal at each frequency in the entire frequency band, which allows for the individual identification of spectral components, particularly those attributable to the patient's physiology (patient contribution). This frequency domain allows for the identification of harmonic components in the flow data, such as the measured flow rate in the venous line 150, and thus the individual identification of contributions to the pulsatile flow rate, including the patient contribution, such as a contribution corresponding to the patient's pulse rate or respiratory rate.

[0062] In general, the present disclosure allows for acquisition of flow data sufficient to allow accurate quantification (discrimination) of components of the flow data, particularly frequency domain components of the flow data. For example, flow data as a function of time is acquired at time intervals short enough to model oscillations, fluctuations, pulsations, or frequency changes in flow individually, and over a period of time sufficient to include multiple occurrences of these. The controller 180 then decomposes this flow data based on the hypothesis that the acquired signal is composed of a sum of individual oscillation components. Thus, the controller 180 can decompose a time-dependent function into a function that depends on spatial or temporal frequencies, and identify the patient contribution to the decomposed frequencies.

[0063] In one configuration, the spectral analysis can be performed by a Discrete Fourier Transform (DFT), specifically a Fast Fourier Transform (FFT). The DFT converts a time domain function into a series of sine waves of various frequencies and reconstructs the signal as a sum of such sine waves. The so-called frequency content spectrum is a frequency domain representation of a signal (e.g., a measured flow rate or a flow waveform or pulsation pattern of the flow data). Frequency analysis provides a different perspective on the flow data related to the flow in the venous line 150. Instead of looking at the flow data (i.e., flow rate in the time domain), frequency analysis breaks down the time data into a series of sine waves. The FFT is a well-known mathematical technique that converts a function of time into a function of frequency. A commercially available spectrum analyzer or a software application integrated into the controller 180 converts the flow data, such as the measured signal intensity pattern of the input signal, into frequency components in a full frequency band.

[0064] Referring to Figure 4, which is an FFT of the venous flow data of Figure 2, there is shown the first harmonic of the pump frequency derived from the flow data in venous line 150. Also shown in Figure 4 is the first harmonic of the heart rate of the patient connected to extracorporeal circuit 100, derived from the flow data in venous line 150, indicating the presence of a patient contribution that may correspond to the patient's pulse rate.

[0065] Referring to Figure 5, which is an FFT result of the arterial flow data of Figure 3, the first and second harmonics of the pump 170 are shown. It is contemplated that these harmonics may also be known or derived from the operating parameters of the pump 170, such as the revolutions per minute of the pump. It is also noted that harmonics of the heart rate are also observed in the arterial flow data. However, it is understood that even if there is an interruption in the flow between the venous line 150 and the patient's circulatory system 30, such as by removal of the venous needle, the harmonics of the heart rate of the arterial line 120 will still remain or be present, since a signal will propagate from the arterial access of the arterial line.

[0066] Referring to FIG. 6 , which shows an overlay of arterial and venous flow data, FFT spectral analysis confirms that contributions from the patient (heart rate) and pump 170 are observed at both flow sensors, flow sensor 126 in arterial line 120 and flow sensor 156 in venous line 150.

[0067] Thus, controller 180 is configured to identify at least one patient contribution to the flow data, such as a calculated or measured flow rate in venous line 150, by applying spectral analysis to the flow data. Controller 180 can then monitor the identified patient contribution and provide alarm notification or pump control in response to a change in the patient contribution (e.g., termination, etc.).

[0068] It should be understood that although this specification describes a Fourier transform being used to decompose the acquired flow data, other signal analysis techniques can also be used to extract information from the flow data regarding the presence or absence of patient contribution to the flow data of the extracorporeal circuit (e.g., venous line 150), particularly the presence or absence of patient contribution resulting from the patient's physiology, in order to monitor the presence or absence of patient contribution in the venous line.

[0069] Referring to FIG. 7, the flow rate of the venous line 150 is shown, including a pulsatile component. FIG. 8 is a graph showing the flow rate of the arterial line 120 of the extracorporeal circuit 100 shown in FIG. 7. FIG. 9 is a spectral analysis result of the flow rate data (specifically, the flow rate) of FIG. 7. In FIG. 10, the harmonics originating from the pump 170 are prominent and shown to be the dominant harmonics. Referring to FIG. 9, while the harmonics originating from the pump 170 are the dominant harmonics, harmonics originating from the patient's physiology, i.e., the patient contribution, can also be identified. That is, in the blood flow rate of the venous line 150, harmonics originating from downstream physiology are identified. Thus, by monitoring the disappearance or change of a predetermined amount of the patient contribution, the controller 180 can detect a disruption of flow from the venous line 150 of the extracorporeal circuit 100 to a patient's blood delivery site, such as the vascular device 200.

[0070] Thus, the system can be configured to monitor an extracorporeal circuit 100 extending from an access device 200, through an extracorporeal blood treatment device 130 (e.g., a dialyzer), and back to the access device. In this configuration, the extracorporeal circuit includes an arterial line 120 extending from the access device to the blood treatment device, a venous line 150 extending from the blood treatment device to a vascular access, and a pump 170 connected to the extracorporeal circuit to pump blood from the access device into the extracorporeal circuit, from the arterial line, through the blood treatment device, through the venous line, and back to the access device. The system also includes a flow sensor 156 for acquiring flow data of blood flow in the venous line 150, and a controller in communication with the flow sensor, the controller 180 being configured to determine the flow rate in the venous line based on the flow rate data, identify at least one patient contribution to the determined flow rate resulting from downstream patient physiology by spectral analysis, in particular FFT, and detect a disruption in the extracorporeal blood circulation circuit downstream of the pump 170 based at least in part on the identified patient contribution. That is, the controller 180 can be configured to identify the disappearance of a previously identified patient contribution as indicated by the spectral analysis. Identifying the disappearance of the patient contribution from the spectral analysis can be used to identify a disruption in the flow from the extracorporeal circuit 100 to the access device 200 (or circulatory system 30) and to issue an alarm, stop the pump 170, or both. As described above, such a disruption can include removal of the venous needle and separation of the access-blood line.

[0071] The controller 180 can perform the above-mentioned transformations to obtain and even compare (monitor) the frequency components. However, it is understood that configurations in which data points are selectively obtained, but because a continuous waveform is required to perform Fourier analysis, the controller 180 can also apply predictive models (such as, but not limited to, AI algorithms) to these spaced data points in addition to the above-mentioned transformations to generate, for example, expected waveform patterns, etc., which can identify disruptions as soon as changes are identified in the time domain. Thus, the controller 180 can identify changes in the patient contribution in the frequency domain, the time domain, or both. It is further contemplated that the controller 180 can identify changes in the correlation between the flow data (e.g., flow waveform patterns) obtained or expected from either or both of the arterial and venous lines and the next obtained or expected pattern (e.g., the pattern that will emerge from the next heart beat).

[0072] The controller 180 can be configured to improve identification of the patient's physiological parameter(s) in the flow data of the blood supply (venous) line 150, such as by correlating the flow data between the blood supply (venous) line and the blood supply (arterial) line 120. For example, the controller is configured to identify at least one patient's physiological parameter (patient contribution) or a change in the patient's physiological parameter from a relationship between the blood supply (venous) line flow data and the blood supply (arterial) line flow data, with one flow sensor 156 operably connected to the blood supply (venous) line 150 to generate the blood supply line flow data and a second flow sensor 126 operably coupled to the blood supply (arterial) line 120 to generate the blood supply line flow data. In one configuration, the relationship is a correlation between the blood supply (venous) line flow data and the blood supply line flow data.

[0073] It will further be appreciated that the controller 180 can receive information from the blood treatment device 130, the pump 170, or both, such as blood flow or revolutions per minute settings, and distinguish between the transform (Fourier) components of the acquired flow data to distinguish between flow data generated by the pump 170 and flow data generated due to patient contributions to the flow data (such as the patient's heart rate).

[0074] The controller 180 is intended to be connected to a flow sensor 156 that senses the flow through the venous line 150. The controller 180 is configured to determine a change in blood flow downstream of the flow sensor in the extracorporeal circuit 100 associated with a disruption between the extracorporeal circuit 100 and the patient's circulatory system 30. Such a change in flow data (i.e., flow rate) in the venous line 150 can be detected as a change in the patient contribution to the flow signal, which is manifested as a change in harmonics detected in the frequency spectrum of the flow signal. It has further been determined that the above-mentioned disruption, particularly venous needle removal or access-bloodline separation, can be accompanied by non-harmonic changes in the flow rate of the extracorporeal circuit 100, particularly spikes that are non-harmonic increases in the flow rate. It is believed that the above-mentioned disruption, particularly the flow rate spike associated with venous needle removal or access-bloodline separation, may be in response to exposure of the venous line 150 to atmospheric pressure, a change in resistance to blood flow, or a combination of both. That is, a temporary spike in flow rate in the extracorporeal circuit 100 may be in response to the venous line 150 being exposed to atmospheric pressure rather than the pressure of the access device 200, such as a venous access. It is further contemplated that a temporary spike in flow rate in the extracorporeal circuit 100 may be in response to a decrease in resistance to blood flow in the venous line following a disruption in the extracorporeal circuit. Thus, a spike in flow rate may be due to a change in pressure to which the flow in the extracorporeal circuit 100 is exposed, a decrease in resistance to blood flow through the venous line 150, or a combination of these factors. A spike in flow rate in the extracorporeal circuit 100 is typically accompanied by an increase in flow rate sensed by the venous flow sensor 156 (a positive spike) and a decrease in flow rate at the dialysate line outflow sensor 336 (a negative spike). The latter is due to the fact that the total volume of the dialyzer compartment of the dialyzer 130 remains constant during the period of the spike in flow rate in the extracorporeal circuit 100.

[0075] With respect to flow rate spikes attributable at least in part to reduced flow resistance, it is noted that, like the central catheter, the tip of the venous catheter of venous line 150 may also be located in close proximity to the right atrium of the heart of the patient's circulatory system 30. When venous line 150 is intentionally disconnected (e.g., along the line connected to the venous catheter), resistance to flow (from the catheter lumen) is reduced and a flow rate spike is observed in extracorporeal circuit 100. It is therefore contemplated that detecting a flow rate spike in venous line 150 may correspond to detecting a particular contribution or characteristic of any blood treatment device in extracorporeal circuit 100 associated therewith.

[0076] Referring to FIG. 11, a bench simulation of IV needle removal using a set of hemodialysis tubing and fittings is shown. It is assumed that the flow data of the venous line 150 from such bench simulation includes a flow spike as a non-harmonic component or non-harmonic change. The flow spike of the venous line 150 in FIG. 11 is associated with the removal of the venous needle. That is, the flow data is assumed to include a non-harmonic change (e.g., increase) in blood flow that is not a change in the patient contribution of harmonics identified for the flow signal measured before and after the spike. Typically, such a flow spike (non-harmonic change) is assumed to be associated with the removal of the venous needle or a separation between the access and blood line. Thus, it is assumed that the increase in flow compared to the average flow before the spike when a spike is observed in the non-harmonic pattern may be due to a pressure change at the end of the blood line that is disconnected between the flow sensor and the patient, such as a dislodged venous needle, a disconnected catheter, etc. Alternatively, it can be surmised that the increase in flow rate relative to the average flow rate prior to the spike observed in the non-harmonic pattern may be due to a change in resistance to flow within the extracorporeal circuit 100, particularly in the venous line 150 distal to the break, or a combination of a pressure change and a change in resistance to flow. Note that in both of these two situations, the pressure change and the resistance change, the patient harmonic contribution to the measured flow rate disappears when the change occurs, but the conclusion that an IV needle removal or access-bloodline separation has occurred is based not on a change in the patient harmonic contribution to the flow rate measured prior to the disruption event, but on the occurrence of an unusual spike in the measured flow rate and the appearance of a temporary non-harmonic change to the average flow rate starting from the abnormal spike.

[0077] 11 is associated with IV needle removal, it is contemplated that not all flow spikes in venous line 150 are associated with or indicative of a disruption such as IV needle removal or access-blood line separation. That is, a flow spike in an extracorporeal circuit 100, such as venous line 150, may not be associated with a disruption such as IV needle removal or access-blood line separation, but may instead be associated with patient movement or other causes such as electronic or electromagnetic noise.

[0078] To address this issue, in one configuration, the controller 180 is configured to apply a threshold (i.e., a predetermined level) to the magnitude of flow spikes (non-harmonic changes in flow rate) in the venous line 150, such that a flow spike greater than the threshold (predetermined level) indicates a possible disruption in flow between the extracorporeal blood circuit 100 and the patient's circulatory system 30 (e.g., venous needle removal or access-bloodline separation), while a flow spike less than the threshold does not indicate a possible disruption. The size and shape of the flow spike may be highly device dependent. In a simulated dialysis treatment configuration such as that shown in FIG. 11, it is contemplated that the threshold may be between 15 mL / min and 30 mL / min. Alternatively, the threshold may be a percentage change in flow rate over a given time (or within or less than a given time). For example, a change in flow rate of at least 5% or 10% or more over a period of less than a second or a few seconds may identify the need for further investigation of the increasing slope of the flow spike. Such studies are performed to conclude whether the flow spike is related to a disruption (such as an access-to-bloodline interruption, IV needle withdrawal, etc.) between the extracorporeal blood circulation circuit 100 and the patient's circulatory system 30. Also, considering the limitations in obtaining real patient disruption data, it is contemplated that a disruption detection algorithm can be developed from bench simulations.

[0079] 11, a very rapid increase in blood flow can be seen, as a spike in flow (non-harmonic change in flow) in (blood inlet) venous line 150 is shown compared to the average blood flow in the venous line, which is relatively constant. The peak value of this flow spike is greater than the pulsation produced in the flow in venous line 150 by the pump, and greater than any flow fluctuations resulting from cardiac pressure fluctuations of the patient at the end of venous line 150.

[0080] Generally, an increasing (positive) spike in flow caused by patient movement or other causes such as electronic or electromagnetic noise is preceded or followed by a decreasing (negative) spike. These differ from the inverted (inverted) sawtooth blood flow spikes shown in FIG. 11, which have a sudden increase followed by a downward slope to drop substantially to the previous average flow rate or within a percentage range specified below. The slope of this increase in flow rate is determined in large part by the low pass bandwidth of the flow sensor 156. The flow spike is a substantially instantaneous response observed when fluid communication between the extracorporeal circuit 100 and the access device 200 (or the patient's circulatory system 30) is interrupted, particularly when the venous line 150 is disconnected from the patient (e.g., the access device). The downward slope of the flow spike would cause the flow rate to decay approximately exponentially back to the pre-spike level or to within 5%, 10%, or 25% of the pre-spike flow rate. Thus, the controller 180 connected to the flow sensor 156 can reliably distinguish a spike caused by a disruption between the extracorporeal blood circuit 100 and the patient's circulatory system 30 from a flow spike caused by patient movement or other causes such as electronic or electromagnetic noise by tracking the average flow baseline and integrating the "area under the blood flow signal curve" above the average flow baseline immediately following the flow spike. For the circuit constructed using the dialysis tubing and fittings used to generate the data shown in Figure 11, the time from the flow spike signal to the sawtooth decay back to the previous peak flow level was approximately 7 seconds, and the area under the curve (integral value) of the flow curve spike during this 7 second period corresponds to approximately 3.5 mL of blood volume. Therefore, in the case of a circulation circuit established using a set of dialysis tubing and fittings to generate the data shown in FIG. 11, the control device 180 can be configured to reliably identify a disruption between the extracorporeal blood circulation circuit 100 and the patient's circulatory system 30 based on the integration result of the blood volume using a pair of integration time spans and corresponding areas under the curve as trigger values, such as a pair of integration time spans of up to 7 seconds and a blood volume of up to 3.5 mL.It is contemplated that the trigger value may be a time span and volume pair that is at least partially dependent on the respective blood treatment device and associated tubing set, such as 1 mL integral over the first 3 seconds, 1.5 mL integral over 5 seconds, etc. Alternatively, the controller 180 may be configured to consider additional parameters in evaluating the flow spike, such as tracking the time (duration) that the flow spike remains above a threshold (or predefined) level. Additionally, the controller 180 may be configured to estimate the overall exponential decay of the spike from its trajectory over the first second or seconds after the spike, and then estimate the total area under the curve of the spike. This facilitates relatively rapid analysis and response to potential disruptions such as IV needle removal, access-bloodline separation, or other disruptions that may impact patient health. The blood flow rate following a flow spike may depend, at least in part, on the type of pump 170. In FIG. 11, the pump 170 is a constant force roller pump, so the measured flow rate returns to a value close to that measured before the spike began. If the pump 170 is a centrifugal pump, it is believed that after a disruption such as removal of the IV needle or separation of the access-bloodline occurs, the flow rate will return to a slightly higher rate (e.g., within a certain percentage range) than before the disruption. The exponential decay of the flow rate after a spike is believed to be related to volumetric changes in components such as the extracorporeal circuit 100 between the constant flow pump 170 and the flow sensor.

[0081] Referring again to FIG. 11, the area under the curve during the spike and its exponential decay is relatively small, approximately 3.5 mL. The amount of blood sensed by the flow sensor 156 above the average flow during the first second of the spike is approximately 0.7 mL, or approximately 20 drops of blood. Thus, to detect disruptions such as IV needle removal or access-bloodline separation, a low noise, high resolution flow sensor with a flow response bandwidth of 5 Hz or 10 Hz is required. It has been determined that the total amount of blood leaking out of the end of the venous line 150 during the first second of the disruption (the first second following the positive spike) is significantly greater, at 330 mL / min x 1 / 60 = 5.5 mL plus the 0.7 mL spike. The present method of monitoring disruptions such as access-bloodline separation or IV needle removal utilizes the high flow resolution of the flow sensor 156 and its flow detection algorithm to quickly identify flow changes.

[0082] 13, a non-harmonic change in the flow rate in the venous line 150, such as a flow rate spike, may correspond to a disruption in the extracorporeal blood circulation circuit 100, particularly the removal of the venous needle or an access-blood line separation, and can be used to stop blood flow from the pump 170. This allows the appearance of a non-harmonic increase or spike in the flow rate in the venous line 150 to be used to identify a disruption between the extracorporeal blood circulation circuit 100 and the patient's circulatory system 30, particularly the removal of the venous needle or an access-blood line separation.

[0083] Specifically, with reference to FIG. 14, the controller 180 can be configured to monitor a flow rate, such as an average flow rate, in the extracorporeal circuit (e.g., venous line 150) and periodically update the average flow rate. The periodic update period can range from one-tenth of a second to one, two, three, five, or more seconds. Spikes can be detected by comparing the flow rate as a function of time to the average flow rate (e.g., subtracting the average flow rate from the most recent flow rate as a function of time). Whether or not a spike is detected can be determined according to the difference between the current flow rate and the average flow rate. If a flow spike is not detected, the controller 180 continues to monitor the flow rate and update the average flow rate. On the other hand, if a spike is detected, the controller 180 can calculate the area under the curve of the spike or identify the shape of the spike in light of known disruptions to determine whether the spike is in response to a disruption between the extracorporeal circuit 100 and the patient's circulatory system 30 (e.g., removal of the venous needle, access-bloodline separation, etc.).

[0084] It is contemplated that the appearance of a flow spike in the extracorporeal circuit 100, such as the venous line 150, can be used alone or in combination with a patient contribution identified in a spectral analysis of the flow data (or at least one of the harmonics indicative of a patient contribution identified in the flow data), to more reliably identify a disruption between the extracorporeal circuit 100 and the patient's circulatory system 30 (particularly a removal of the venous needle or an access-blood line separation).

[0085] Thus, the controller 180 may be configured to identify a disruption between the extracorporeal circuit 100 and the patient's circulatory system 30, in particular an IV needle removal or an access-bloodline separation, based on or from non-harmonics identified in the extracorporeal circuit flow rate, or harmonics indicative of patient contribution identified in such flow rate data, or a combination of non-harmonics and harmonics indicative of patient contribution. It is believed that the combination of an increase in non-harmonics in the flow rate data and (the loss of) harmonics indicative of patient contribution may reduce the rate of false positives of a disruption between the extracorporeal circuit 100 and the patient's circulatory system 30, in particular an IV needle removal or an access-bloodline separation.

[0086] It is further contemplated that the flow rate of the extracorporeal circuit 100 may be monitored or measured on the dialysate side 302 of a blood treatment device 130, such as a dialyzer, as shown in FIG. 1. An increase in pressure on the blood side of the dialyzer 130 increases the blood volume inside the fibers of the dialyzer 130, which causes a compensating decrease in the dialysate volume that changes the volume of dialysate surrounding the dialyzer fibers inside the dialyzer 130 housing. It is contemplated that the dialysate flow rate can thus determine the flow rate in the extracorporeal circuit 100. Conversely, a negative spike in the flow rate in the dialyzer 130 causes a decrease in the volume of fluid inside the dialyzer fibers, which causes a compensating increase in the volume of dialysate surrounding the dialyzer fibers inside the dialyzer housing. The controller 180 can monitor the change in dialysate volume by subtracting the difference between the dialysate flow rate into and out of the dialysate 130 simultaneously (e.g., by a dialysate inflow flow sensor 326 sensing the flow rate in the dialysate inflow line 320 and a dialysate outflow flow sensor 336 sensing the flow rate in the dialysate outflow line 330) and integrating the difference between the two measurements over a given time period after a spike in the dialysate flow is recorded to derive the change in dialysate volume. Furthermore, because the dialysate flow in the dialysate inflow line 320 is generated by a pump 340, such as a roller pump, having an output flow rate that is largely independent of the pump outlet pressure, it is contemplated that the change in the dialysate volume of the dialysate 130 can be measured in a simple manner by simply integrating the change in the dialysate outflow line flow recorded by the dialysate outflow flow sensor 336 over a period of time after a dialysate flow spike is recorded by the dialysate outflow flow sensor 336. Recordings of dialysate flow spikes and associated volume changes can be used alone or in combination with harmonics indicating patient contributions identified in the blood supply line 150, non-harmonics identified in the blood supply line 150, or both, to detect disruptions between the extracorporeal blood circulation circuit 100 and the patient's circulatory system 30 (e.g., removal of the venous needle, access-blood line separation, etc.).Accordingly, the present disclosure contemplates identifying a disruption in the connection between the blood supply line of the extracorporeal circuit 100 and the patient's circulatory system 30 in response to a non-harmonic decrease in the dialysate flow rate in the dialysate outlet line 330 of the blood treatment device 130. The controller 180 may be in communication with the dialysate outlet flow sensor 336, or with both the flow sensor 326 and the flow sensor 336. In that case, the controller is configured to (i) detect a disruption between the extracorporeal circuit 100 and the patient's circulatory system 30 based at least in part on a non-harmonic change in at least the dialysate flow rate out of the blood treatment device 130, or the dialysate flow rate into or out of the blood treatment device 130.

[0087] As described above, the extracorporeal circuit 100 can be a blood treatment circuit, such as a dialyzer 130, configured to controllably transfer solutes and water through a semipermeable membrane separating the blood flow and the dialysate flow, or an extracorporeal life support device, such as an extracorporeal membrane oxygenator (ECMO). Thus, in the case of an ECMO circuit, the flow sensor 156 can sense blood flow in the blood line 150 to detect blood flow spikes, which can be used to identify disruptions to blood flow or return to the patient and control the pump 170 in the extracorporeal circuit 100 accordingly.

[0088] Thus, the flow data may include non-harmonic components, such as spikes or temporary increases in flow rate, and harmonic components resulting from patient contributions in the flow rate data, and the controller 180 is configured to identify a disruption in the connection of the extracorporeal blood circulation circuit 100, in particular removal of the venous needle or access-blood line separation, in response to (i) at least one non-harmonic component in the flow rate, or (ii) at least one harmonic component in the flow rate, or (iii) a combination of harmonic and non-harmonic components in the flow rate.

[0089] In an optional configuration, the non-harmonic change in blood flow in the extracorporeal circuit 100, and particularly in the blood delivery line 150, is a temporary increase in measured or local blood flow. Thus, the controller 180 can be configured to identify an increase in blood flow corresponding to a set of volumes and durations that depend at least in part on the respective blood treatment device and associated tubing set, such as an integral of at least 1 mL over the first 3 seconds, or an integral of at least 1.5 mL over 5 seconds, and can be used to identify a disruption in the extracorporeal blood circulation circuit 100, particularly a removal of the venous needle or an access-blood line separation.

[0090] The system provides a method that includes identifying a disruption (e.g., by an access device 200, etc.) between the venous line 150 of the extracorporeal circuit 100 and the patient's circulatory system 30. Such a disruption involves a change in pressure in one of the venous line 150 and the dialyzer 130, and a step change in volume associated with one of the venous line 150 and the dialyzer 130, or a change in flow rate through one of the venous line 150 and the dialyzer 130.

[0091] The system also provides a further method including identifying at least one patient contribution in the measured flow rate in the venous line 150 of the extracorporeal circuit 100 resulting from downstream patient physiology, and monitoring changes in the patient contribution following a spike in the measured flow rate to identify disruptions in vascular access between the extracorporeal circuit 100 and the circulatory system 30. The monitoring step can include monitoring the rate of change of the measured flow rate relative to a predetermined level or threshold, as well as monitoring for the presence or absence of waves in the measured flow rate identified as harmonics.

[0092] The disclosed method includes measuring the flow rate in venous line 150 and identifying a disruption in the connection between the venous line and the patient's circulatory system 30 in response to a change in a flow component corresponding to a physiological parameter of the circulatory system connected downstream to the venous line. The change in the component can be detected by a corresponding change in a spectral analysis of the measured flow rate in venous line 150. Thus, the change in the component can be detected by a corresponding change in a harmonic of the spectral analysis of the measured flow rate in venous line 150.

[0093] The disclosed method also includes measuring the flow rate in the venous line 150 and identifying a disconnection between the venous line and the patient's circulatory system 30 in response to a change in a component of the flow rate corresponding to a parameter of the circulatory system connected downstream to the venous line (e.g., the patient's mean blood pressure, heart rate, or respiratory rate, etc.). The change in the component can be detected by a corresponding instantaneous change in the measured flow rate in the venous line 150 or the dialysate line 330. The change in the component can thus be detected by a corresponding instantaneous change in non-harmonic spikes in the flow rate and further by the disappearance of the identified harmonic pattern in the measured flow rate.

[0094] Thus, in one configuration, the present disclosure provides for monitoring an extracorporeal blood treatment device 130 of an extracorporeal circuit 100, the extracorporeal circuit including an arterial line 120 with a patient arterial connection and a venous line 150 with a patient venous connection, a dialyzer 130 and associated dialysate circuit 310 with a pump 340, a dialysate inlet line 320 and a dialysate outlet line 330, and a pump 170 for transporting blood through the extracorporeal circuit. The method includes measuring flow rates in at least one of the venous line 150 and the dialysate outlet line 330 of the extracorporeal circuit 100, identifying at least one patient contribution in the measured flow rate that corresponds to a downstream patient physiological parameter, and determining the occurrence of a flow interruption between the extracorporeal circuit 100 and the circulatory system 30 in response to a change in the patient contribution to the measured flow rate. Analysis of the measured flow data in identifying changes in patient contribution may include calculation of the average flow (mean flow rate) and spikes in the average flow, calculation of the flow rate as determined by the integral of the change in the average flow over a period of time from when the spike in the average flow occurs, and spectral analysis to identify frequencies that correspond to downstream patient physiology, which may trigger an alarm or shut down the pump 170.

[0095] The present disclosure provides a method for determining whether a disruption has occurred in the flow from the extracorporeal circuit 100 to the patient's circulatory system 30 by identifying an associated spike in the dialysate flow from the blood treatment device 130, particularly if the spike corresponds to a decrease in dialysate flow from the blood treatment device, and more particularly if the spike in dialysate flow rate from the blood treatment device is accompanied by at least one of a spike in flow rate in the blood (venous) line 150 and a change in the patient's contribution to the blood line flow. Accordingly, the present disclosure contemplates that the controller 180 is connected to the dialysate outlet flow sensor 336 in the dialysate circuit 310 and configured to identify the disruption in response to a spike in dialysate flow rate, particularly a decrease in the dialysate flow rate in the dialysate outlet line 330, and that the controller can be configured to use non-harmonics of the flow rate in the venous line 150, harmonics of the blood flow rate in the extracorporeal circuit, or both, to identify or confirm the disruption.

[0096] The present disclosure describes systems and methods for determining whether there is an interruption in flow from the extracorporeal circuit 100 to the patient's circulatory system 30, such as when a needle or cannula becomes dislodged from the patient or when a blood treatment device 130 is disconnected from an IV needle or venous catheter lumen. That is, an interruption in flow from the extracorporeal circuit 100 to the patient's circulatory system 30 includes an interruption in flow within the extracorporeal circuit downstream of the pump 170. For example, such interruptions may include an interruption in flow from the pump to the venous line 150, or from the blood treatment device 130 to the venous line, as well as an interruption between the venous line and the patient access, or from the patient access 200 to the circulatory system 30.

[0097] One of the primary applications of the present system and method is blood therapy, in which blood is removed from a patient, treated, and the treated blood is returned to the patient. As mentioned above, typical blood therapies include hemodialysis ("HD") systems, hemofiltration ("HF") systems, hemodiafiltration ("HDF") systems, and continuous renal replacement therapy ("CRRT") systems, all of which remove blood from a patient, filter the blood, and then return the blood to the patient. However, it is understood that the access disruption detection system and method described herein can be used in these blood therapies as well as in cardiopulmonary bypass surgery, in which blood is removed from a patient, oxygenated, and then returned to the patient. Furthermore, the present disruption detection method can also be used in single-needle systems, such as certain types of drug delivery systems that infuse medication from a source into a patient. Additionally, the present disruption detection method can also be used in systems that separate and collect blood (e.g., to separate platelets, plasma, red blood cells, or cell subpopulations), such as single-needle or dual-needle apheresis therapy.

[0098] Accordingly, the present disclosure provides a method that includes the steps of (a) identifying a patient contribution in flow data of the blood delivery line 150 of the extracorporeal circuit 100 that is due to downstream patient physiology, and (b) monitoring the patient contribution to identify a disruption of flow between the extracorporeal circuit and the patient's circulatory system 30. The method may also further include generating an alert or alarm upon identifying the disruption.

[0099] Accordingly, the present disclosure provides a method including the steps of (a) acquiring flow data of a blood supply line 150 in an extracorporeal circuit 100 having a pump 170 providing flow to the blood supply line 150, and (b) identifying a disruption in connection between the extracorporeal circuit and a downstream patient's circulatory system 30 in response to a non-harmonic component of the flow data.

[0100] The present disclosure further provides a method for monitoring an extracorporeal blood treatment device including an extracorporeal circuit 100. The extracorporeal circuit includes an arterial line 120 having a patient arterial connection, a venous line 150 having a patient venous connection, and a pump 170 for transporting blood through the extracorporeal circuit. The method includes the steps of (a) sensing blood flow data in the venous line of the extracorporeal circuit, (b) identifying a patient contribution in the sensed blood flow data that corresponds to a downstream patient physiological parameter, and (c) determining a disruption of connection between the extracorporeal circuit and the circulatory system 30 in response to the identified change in the patient contribution to the sensed blood flow data. The method may also further include generating a control signal to activate an alarm unit, stop the pump 170, or both, after determining the occurrence of the disruption.

[0101] Although the present disclosure has been described in detail above, particularly with reference to one embodiment, it will be understood that variations and modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. The scope of the present invention is defined by the appended claims, and it is intended to embrace all modifications that do not depart from the meaning and scope of equivalents. [Explanation of symbols]

[0102] 30 Patient's Circulatory System 100 Extracorporeal circulation circuit, extracorporeal blood circulation circuit 110 Patient's blood drainage site 120 Arterial line, blood drainage line 126 Arterial Flow Sensor 130 Blood treatment devices, dialysis machines 150 Intravenous lines, blood supply lines 156 Venous Flow Sensor 160 Patient blood supply site 170 Pump 180 Control device 200 Access Devices, Vascular Devices, Patient Access 302 Dialysis fluid side 310 Dialysate circuit 320 Dialysis fluid inflow line 326 Dialysis Fluid Inflow Flow Sensor 330 Dialysis fluid drain line 336 Dialysis fluid discharge flow sensor 340 Pump

Claims

1. In a system for detecting a break in the fluid connection between an external circulation circuit and a patient's circulatory system, (a) an extracorporeal circulation circuit extending from the patient's circulatory system through a blood withdrawal site of the patient to an extracorporeal blood treatment device and back to the patient's circulatory system through a blood return site of the patient, the extracorporeal circulation circuit comprising a blood withdrawal line extending from the blood withdrawal site of the patient to the blood treatment device, a blood return line extending from the blood treatment device to the blood return site of the patient, and a pump configured to pump blood through at least a part of the extracorporeal circulation circuit; (b) a flow sensor configured to acquire flow rate data of the flow in a part of the extracorporeal circulation circuit; (c) a control device in communication with the flow sensor, (i) identifying a non-harmonic change in the flow rate data, (ii) when a break in the fluid connection between the extracorporeal circulation circuit and the patient's circulatory system is detected based at least in part on the non-harmonic change identified in the flow rate data, transmitting a control signal configured to instruct the system to perform at least one of activating an alarm unit or stopping the pump; a control device configured as such; a system comprising the same.

2. The system according to claim 1, wherein the flow sensor acquires the flow rate data from the blood return line.

3. The system according to claim 1, wherein the flow sensor is a dialysate drainage flow sensor configured to sense the flow in a dialysate drainage line fluidly connected to the blood treatment device.

4. The system according to claim 1, wherein the control device is further configured to detect the break in accordance with at least one of (i) the non-harmonic change in the flow rate data being an increase in the non-harmonic and (ii) the non-harmonic change in the flow rate data being a decrease in the non-harmonic.

5. The system according to claim 1, wherein the control device is further configured to detect the break in accordance with at least one of (i) the non-harmonic change being an increase in the non-harmonic in the blood flow rate having an increase rate higher than a first predetermined rate and (ii) the non-harmonic change being a decrease in the non-harmonic in the dialysate flow rate having a decrease rate greater than a second predetermined rate.

6. The system according to claim 1, wherein the control device is further configured to detect the interruption in accordance with at least one of: (i) the change in the non-harmonic wave being an increase in the non-harmonic wave that maintains an increase in flow rate over a time longer than a predetermined time; and (ii) the change in the non-harmonic wave being a decrease in the non-harmonic wave in the dialysate flow rate that maintains a decrease in the dialysate flow rate over a time longer than a second predetermined time).

7. The system according to claim 1, wherein the control device is further configured to detect the interruption in accordance with the area under the curve of the change in the non-harmonic wave over a given time.

8. The system according to claim 1, wherein the control device is configured to identify a harmonic wave in the flow rate data and is configured to detect the interruption in accordance with the identified change in the non-harmonic wave and the identified harmonic wave.

9. The system according to claim 1, wherein the interruption is one of removal of the intravenous injection needle and separation between the access - blood line.

10. The system according to claim 1, wherein the control device is configured to stop the pump in response to detection of the interruption.

11. In a method for detecting an interruption in a fluid connection between an extracorporeal circulation circuit and a patient's circulatory system, (a) monitoring an extracorporeal circulation circuit that extends from the patient's circulatory system through the patient's blood withdrawal site to an extracorporeal blood treatment device and returns to the patient's circulatory system through the patient's blood delivery site, the extracorporeal circulation circuit comprising a blood withdrawal line extending from the patient's blood withdrawal site to the blood treatment device, a blood delivery line extending from the blood treatment device to the patient's blood delivery site, and a pump configured to pump blood through at least a part of the extracorporeal circulation circuit; (b) identifying a change in a non-harmonic wave in flow rate data of a part of the flow in the extracorporeal circulation circuit; (c) detecting an interruption in the connection between the blood delivery line of the extracorporeal circulation circuit and the patient's circulatory system in accordance with the identified change in the non-harmonic wave in the flow rate of the part of the extracorporeal circulation circuit; (d) transmitting a control signal configured to command execution of at least one of activation of an alarm unit or stopping of the pump when an interruption in the fluid connection of the blood delivery line between the extracorporeal circulation circuit and the patient's circulatory system is detected; A method comprising the above steps.

12. The change in the non-harmonic wave in the flow rate of the part of the extracorporeal circulation circuit is identified in the flow rate data from the flow sensor, the flow sensor being, (i) the dialysate flow exiting the blood treatment device of the extracorporeal circulation circuit, and (ii) the blood flow rate in at least one of the blood withdrawal line of the extracorporeal circulation circuit and the blood delivery line of the extracorporeal circulation circuit is configured to obtain flow rate data of at least one of them, the method according to claim 11. **Claim 13** The change in the non-harmonic wave in the flow rate of the extracorporeal circulation circuit is identified in the flow rate data from the flow sensor, the flow sensor being, (i) the dialysate flow exiting the blood treatment device of the extracorporeal circulation circuit, and (ii) the blood flow rate in the blood delivery line of the extracorporeal circulation circuit is configured to obtain flow rate data of at least one of them, the method according to claim 11. **Claim 14** The method further includes the step of identifying a harmonic wave in the flow rate data, the harmonic wave corresponding to the patient contribution to the flow rate data, the method according to claim 12. **Claim 15** The interruption is one of the removal of the intravenous injection needle and the separation between the access and the blood line, the method according to claim 12.

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